Grille insert



FIG. 1 is a front perspective view of a grille insert showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

It will be understood that the broken lines shown in the drawings illustrate portions of the grille insert that form no part of the claimed design. 

CLAIM The ornamental design for a grille insert, as shown and described. 